Copying-printing apparatus

ABSTRACT

An electrophotographic copier unit and an offset printer unit are combined together to constitute a copying-printing apparatus in accordance with the principles of the present invention, which utilizes an electrophotographic process to accomplish offset printing, utilizes preferably the wet type development to develop an electrostatic latent image, and utilizes an image transfer system to transfer the developed image to a transfer sheet. Such transfer sheet may in turn be used as an offset master sheet. Thus, the apparatus can perform copying and printing operations at high speeds and produce multiple copies in a short time and in an economical and hygienical manner.

United States Patent [191 Yamaji et al.

[ COPYING-PRINTING APPARATUS [75] Inventors: Keizo Yamaii, Tokyo; AkiraKurahashi, Yokohama, both of Japan [73] Assignee: Canon KabushikiKaisha, Tokyo,

Japan [22] Filed: Feb. 28, 1972 [21] Appl. No.: 229,884

[30] Foreign Application Priority Data v Mar 4, 1971 Japan 46-11732 [52]US. Cl 101/132, lOI/DIG. 13, 101/451 [51] Int. Cl B411 11/08 [58] Fieldof Search lOI/DIG. 13, 132, 450, 101/451 [56] References Cited UNITEDSTATES PATENTS 2,357,809 9/1944 Carlson 101/D1G. 13 3,045,587 7/1962Schwertz..... l0l/DlG. 13 3,052,213 9/1962 Schaffert..... lOI/DIG. 133,364,857 l/1968 Lein ct al lOl/451 .1 July 2', 1974 3,451,336 6/1969Mignone l0l/l32.5 3,491,684 l/l970 Borinsky l0l/l32 3,648,603 3/1972Kaminstein l [01/450 X 3,682,095 8/1972 Kaminstein l0l/450 X PrimaryExaminer-Robert E. Pulfrey Assistant Examiner-E. H. Eickholt Attorney,Agent, or Firm-Fitzpatrick, Cella, Harper & Scinto [57] ABSTRACT Anelectrophotographic copier unit and an offset printer unit are combinedtogether to constitute a copying-printing apparatus in accordance withthe principles of the present invention, which utilizes anelectrophotographic process to accomplish offset printing, utilizespreferably the wet type development to develop an electrostatic latentimage, and utilizes an image transfer system to transfer the developedimage to a transfer sheet. Such transfer sheet may in tum be used as anoffset master sheet. Thus, the apparatus can perform copying andprinting operations at high speeds and produce multiple copies in ashort time and in an economical and hygienical manner.

12 Claims, 4 Drawing Figures COPYING-PRINTING APPARATUS BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention relates to acopying apparatus, and more particularly to an apparatus which comprisesa novel combination of an electrophotographic copier and an offsetprinter.

2. Description of the Prior Art Multiple copies have heretofore beenaccomplished by repeating the copying cycle in a copying apparatus ofthe offset printing type or of the electrophotographic type.

In case of the former type, enormous energy and time was required toprepare an offset master and to mount such master on an offset printerbefore it is ready for operation, and these procedures required muchskill.

The latter type of apparatus is superior to the former type in that suchcomplex procedures are not involved in operation, but it still sufferedfrom limitations in copying speed as is usual with theelectrophotographic process, and thus this type has not been suitablefor producing multiple copies within a short period of time. Moreover,the developing means employed with such copying apparatus is preferablyof the wet or liquid type so as to attain simplification of the processand an increase in the copying speed. The wet type development employsan organic solvent as the carrier, and the supply of such carrier alsopresents a problem because a considerable amount of the solvent isconsumed for multiple copies. There is a further problem because most ofthe carrier so consumed is discharged into the atmosphere, causing airpollution, which is hygienically very harmful.

Also known is a system which comprises a combination of offset printingand electrophotography. This system employs a sheet containing zincoxide as a photosesitive medium for electrophotography, on which anelectrostatic latent image is formed, developed and fixed, whereafterthe said sheet is subjected to a hydrophilic treatment (the treatment toimpart a hydrophilic property) and used as a master sheet. In otherwords, this system may be called a direct type in which a photosensitivesheet directly serves as a master sheet. According to such a direct typeof system, the use of a photosensitive sheet also as a master sheetmakes the various means for the latent image formation, development,fixing, etc. very complicated in construction. In addition, the mastersheet becomes very costly because it must have the electrophotographicsensitivity, which a master sheet usually does not need, unless alsoused as a photosensitive sheet. The master sheet suffers from anotherproblem because the zinc oxide material usually forming such sheet,exhibits the great difficulty in the hydrophilic treatment, andreadiness for such treatment is desirable for the master sheet.

SUMMARY OF THE INVENTION It is, therefore, a primary object of thepresent invention to provide an improved copying-printing apparatuswhich can accomplish copying and printing at very high speeds.

It is another object of the present invention to provide acopying-printing apparatus which is especially convenient for producingmultiple copies.

It is still another object of the present invention to provide animproved copying-printing apparatus which can produce multiple printedcopies with a reduced consumption of solvent during theelectrophotographic process and, accordingly, with a reduced amount ofgas produced from the solvent, thus minimizing the environmentalpollution.

It is yet another object of the present invention to provide an improvedcopying-printing apparatus in which a master sheet may be prepared bythe image transferred from the electrophotographic means so as tofacilitate the selection of the materials for the master sheet.

It is still another object of the present invention to provide animproved copying-printing apparatus which can effect copying andprinting very economically.

The invention will now be outlined hereunder. The recording medium usedwith the copying-recording means is formed of an inorganic or organicphotoconductive material such as is normally used for theelectrophotographic process and may take the form of a rotatable membersuch as rotatable drum or endless belt.

The electrophotographic process utilized with the present invention maybe either of the direct type in which the image'is directly copied andfixed on a photosensitive sheet or of the indirect or transfer type inwhich the image isfinally fixed on a transfer sheet. However the lattertype is preferred by the present invention.

The reason is that, in an application of electrophotographic means foroffset printing, if the direct type or electrophotographic sensitivesheet is also used as the offset master sheet, such sheet must satisfynot only the conditions as a master sheet but also the requirement ofsensitivity as an electrophotographic sensitive sheet, and thus, thesheet becomes costly and makes the apparatus more complicated inconstruction. In contrast, since the present invention utilizes thetransfer type, i.e. electrophotographic transfer type of sheet as themaster sheet,the material forming such sheet may be more freely selectedso that the sheet may work well as a transfer sheet and a master sheet,respectively, and this leads to a simplified construction of theapparatus and a lower cost of the master sheet.

The transfer type of electrophotographic process, best suitable for usewith the present invention, is the well-known one as disclosed in US.Pat. No. 2,221,776 issued to Carlson, 1938, wherein a photosensitivemedium comprising a layer of photoconductive material superposed on anelectrically conductive back-up member is charged uniformly over thesurface thereof, which surface is then illuminated by image light toform an electrostatic latent image thereon, whereafter such latent imageis developed with the aid of toner particles and then fixed by heat orsolvent or transferred to separate paper or the like for fixing. Othervarious types of electrophotographic processes may be equally applicableto the present invention.

In either of these electrophotographic processes, the

electrostatic latent image formed on the photosensitive medium isvisualized by developing means, whereafter the developed image istransferred to an offset printing master sheet. The master sheet withthe image thus transferred thereto is wrapped securely around arotatable member such as a master sheet holder drum or belt. ifrequired, the toner image on the master sheet may then be fixed, andthereafter subjected to a hydrophilic and oil-proofing treatment, andthen developed with the aid of printing ink, which in turn istransferred to other transfer sheet.

The developing method may be either of the dry type or of the wet type,but the latter type, i.e. liquid development is preferred by the presentinvention. One reason for this is that the dry type development requiresthe developing means to be considerably complex in construction, andfurther requires an infrared heater to be used for the fixing step.Another reason is that the dry type development limits the speed atwhich the developing and fixing steps are effected. In contrast, the wettype development only requires a very simple construction of thedeveloping means and eliminates the fixing step, which contributes to ahigher developing speed. Especially in the present invention, whichutilizes the electrophotographic process of the transfer type to preparethe master sheet, the wet type development is advantageous over the drytype in that the resolving effect of the image during the image transferstep is superior, thus providing a clearer offset printed image.

As described hitherto, the present invention utilizes electrophotographyto accomplish the offset printing, and utilizes the wet or liquid typedevelopment to develop a latent image, and utilizes the image transfersys tem to transfer the developed image to a transfer sheet, which inturn is used as an offset master sheet. In this regard, thetransfer-master sheet is highly effective inasmuch as the conditionsrequired for such sheet to be used for the transfer ofliquid-developed'image are just in coincidence with the conditionsrequired for such sheet to be used for the purpose of offset printingafter being subjected to a hydrophilic treatment. In a furtherembodiment of the present invention, such a transfermaster sheet mayalso be used as a sheet to be offsetprinted. Again in this case, theconditions therefor are well in accord with the conditions required forsuch sheet to be used for the offset printing.

BRIEF DESCRIPTION OF THE DRAWINGS- The invention will become more fullyapparent from the following detailed description thereof taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of the copyingprinting apparatus ofthe present invention wherein a master sheet also serves as a sheet tobe printed;

FIG. 2 schematically illustrates the copying-printing apparatus of thepresent invention wherein a web for the master sheet is stored in amaster sheet holder drum;

FIG. 3 is a schematic representation of the copyingprinting apparatus ofthe present invention wherein a master sheet supply station is separatefrom the printing sheet supply station; and

FIG. 4 illustrates the method of testing the solvent resistivity of themaster sheet, usable with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, aphotosensitive drum, designated by numeral 1, is rotatable in thedirection of the arrow, and may be electrostatically charged uniformlyover the entire surface thereof by charger means 2. An optical system 3is provided to project image light therethrough from an original ontothe surface of the photosensitive drum 1. An electrostatic latent imageformed on the photosensitive drum 1 in accordance with the originalimage may be developed by developing means 5, which may be of the liquidtype as shown, or of the dry or other suitable type. The image on thephotosensitive drum 1, thus developed by the described process, may betransferred therefrom to a master sheet 8 held on and'over a mastersheet holder drum 7. To enhance the efficiency of such image transfereffect, the master sheet holder drum 7 may preferably be in the form ofan electrically conductive drum for applying or grounding the transfervoltage. Such an electrically conductive drum may be provided by arotatable drum covered with an electrically conductive rubber materialwhich is .commercially available. The master sheet 8 may be held on theholder drum 7 in advance of the transfer process, or alternatively themaster sheet may be held on the holder drum 7 as it is fed for imagetransfer into the nip between the drums l and 7. Holder means for thispurpose is provided as designated at 9. The master sheet 8 now having atoner image transferred thereto may then be subjected to a hydrophilictreatment by water supply means 10, whereafter ink is supplied only tothetoner image area (oleophilic) of the master sheet on the drum fromoleophilic ink supply means 11. The oleophilic ink may be a paste-likemixture of pigment and printing varnish prepared by boiling linseed oil,resin type ink or the like. The master sheet holder drum 7 may continueto rotate so that the image thereon may be transferred onto a web oftransfer paper 13 as fed from a printing sheet supply means 12. In theembodiment shown in FIG. 1, the master sheet 8 for offset printing iscommon with the transfer sheet 13 and this provides a limited variety ofthe material available for such a common printing and master sheet, butalso provides a simplified construction of the apparatus. The materialsuitable for such master sheet may be a paper master which has alreadybeen subjected to a water-proofing treatment.

Since the image transferred from the master sheet 8 to the printingsheet 13 is a printed image, the printing sheet 13 with such transferredimage, may be separated from the master sheet by separator means of theair blast type or the like, and discharged onto a tray 15.

The above-described steps may be repeated for the master sheet drum 7 tothereby obtain the number of copies, as desired.

The copying operation using the described system enables a number ofcopies to be provided irrespective of the limited processing timeusually required in the electrophotographic process, and the solventtreatment may be greatly reduced, thus resulting in a higher speed and ahigher efficiency of the copying operation.

When a desired number of copies has been obtained, the master sheet 8may be released from the master sheet holder means 9 on the master sheetdrum 7 and removed outwardly by separator means.

After the image transfer from the photosensitive drum 1 to the mastersheet 8 has been completed, the photosensitive drum 1 may be cleaned bycleaning means 20 and thereafter, during the offset printing process,may rotate at a high speed with no further image formed thereon andcooperate with the transfer drum 7 to hold the printing sheettherebetween for the impression on such sheet.

FIGS. 2 and 3 show further embodiments of the present invention. Ascompared with the FIG. 1 embodiment in which the master sheet and theprinting sheet are used in common, the embodiment of FIG. 2 is such thata supply roll of master sheet is contained within the master sheetholder drum so that only a desired amount of the master sheet may be fedfor use from a first roll 16 onto the surface of the drum and that afterused, such amount of the master sheet may be taken up on a second roll17 which is also contained within the drum. The printing sheet supply inthis embodiment may be accomplished in the same manner as that describedwith respect to FIG. I. In the embodiment shown in FIG. 3, master sheetsupply means 18 is provided separately from printing sheet supply means19.

As will be seen, the embodiments of FIGS. 2 and 3 are a little morecomplicated in construction than the embodiment of FIG; 1, whereas theuse of a discrete master sheet and printing sheet, for example, a sheethaving a hydrophilic property and containing zinc or aluminum, leads toa wider range for selecting the materials for such sheets, whichparticularly gives rise to a merit that a number of copies may beobtained at a lower cost in spite of the cost of the master sheet suchas zinc or aluminum sheet.

The copying-printing apparatus of the present invention has beendescribed the foregoing detailed description. Now, description will bemade of a master sheet, which is most suitable for use with the presentinvention, when carried out in the form of a liquid developing system.The liquid developer in use may be similar to the wet-type developer-asusually employed in the art of electrophotography. More particularly,the liquid developer may be composed of a carrier liquid having aspecific volume resistivity of lOQcm or more and a toner dispersedtherein, so that the liquid may not destroy the electrostatic latentimage during the developing step and that the toner particles may beselectively deposited in accordance with the electric charges carried bythe electrostatic image. If required, a dispersing agent may further becontained in the developing liquid.

The master sheet applicable for the present invention must satisfy thequalifications given below.

[I] Firstly, such sheet must have a suitable degree of resistivity to asolvent. For the liquid developer, use has chiefly been made of anorganic solvent of high resistivity having the above-describedcharacteristic, such as an organic paraffin solvent such as liquidousparaffin or liquidous isoparaffin, for example. An. organic isoparaffinsolvent is commercially available under the tradename of lsopar, H, G orL" from Esso Chemicals Inc.

of the United States. A developer containing such solvent, when used forthe purpose of image transfer, would therefore encounter the followinginconveniences, unless the master sheet is provided with a suitabledegree of solvent resistivity:

I. If the master sheet is provided with none, or an insufficient solventresistivity, the organic solvent tends to permeate through the transferpaper during the image transfer step, thus resulting not only in ablurred or unsatisfactory image transfer effect but also in anunnecessarilygreat consumption of the developing liquid and a bad dryingeffect.

2. If the master sheet is provided with an excessive resistivity tosolvent, it is desirable during the image transfer step that the solventresistivity imparting substance be suitably softened in the interfacewith respect to the carrier liquid contained in the developer so thatthe toner material from the developer maybe contained therewith. Anyexcessive resistivity to the solvent would reduce the affinity to thecarrier liquid, which in turn would aggravate the fixing effect of thedeveloper and, accordingly, the transferred image could be destroyed asby friction even after being dried.

For these reasons, the master sheet must maintain a suitable degree ofsolvent resistivity, the range of which may be determined by a method,as will be described hereunder. As shown in FIG. 4, a sample sheet 21for test is set on a metallic frame 22. A solvent dripping injector 24is horizontally fixed to a support 26, whereafter a micrometer 25 isgradually rotated to let a drop of solvent (such as Isopar G produced byEsso Chemicals Inc.) onto the sample sheet. At the point of time whenthe drop of solvent has reached the sample surface, a stop watch isstarted. The stop watch is stopped at the point of time when the solventhas permeated throughout the area of the sample sheet, which is occupiedby that drop of solvent (10 to 15 mm diameter). The length of timebetween these two points of time is adopted as a measure for the solventresistivity. The distance from the needle end of the injector to thesurface of the sample sheet may suitably be of the order of 5 cm. Whenmeasurement is carried out in this way, a sample having no resistivityto the solvent permits a drop of solvent to instantaneously permeatethroughout the area of the sample sheet corresponding to the dimensionsof the drop, thus providing a completely permeated condition. On theother hand, a sample having some solvent resistivity only permitsgradual penneation of the solvent, and the length of time required untila drop of solvent has completely permeated through the thickness of thesample and throughout the area thereof corresponding to the size of suchdrop is variable with the degree of the solvent resistivity possessed bythe sample. The solvent dripping injector may have a volume of 1 cc. or2 cc. and its needle may be of A; type. One drop of solvent dripped fromsuch injector has a volume of approximately 0.004 cc. When measured bysuch a method, the solvent resistivity suitable as the master sheet maypractically be in the range of 0.14 to 25 seconds, and preferablyin therange of l to 12 seconds. i

[ll] Secondly, the master sheet must have a suitable degree ofsmoothness. As the result of the test effected in accordance withtheforegoing' method on master sheets with various degrees of smoothness(i.e. the smoothness as measured of the paper grade J IS P8119 by a Bekktester), it has been found that a smoothness in the range of 25 toseconds is satisfactory. Any degree of smoothness less than 25 secondswould cause non-uniformity of the image transfer, unless a great deal ofdeveloping liquid is present, thus resulting not only in anunsatisfactory transferred image but also in a much longer time requiredfor drying up the developingliquid on such image. Conversely, any degreeof smoothness exceeding 150 seconds has proved that a good transferredimage may be obtained with little developing liquid, but the fixingeffect subsequent to the transfer process is adversely affected, thusresulting in destruction of the transferred image due to friction. Thesmoothness may be adjusted to a suitable degree by application'of acoating material, but more practi- Cally-by physical means such as supercalender, machine calender or the like.

Various materials and conditions were studied in order to obtain amaster sheet satisfying the requirements of the solvent resistivity andsmoothness as measured by the above-described method, and as the result,examples shown below were found satisfactory.

EXAMPLE 1 EXAMPLE 2 Vinyl acetate emulsion similar to that of EXAMPLE 1was applied to a raw sheet of paper by size pressing, thereby obtaininga master sheet. The weight of the resin content was at the rate of 2 to3 g/m EXAMPLE 3 2.5 parts by weight of emulsion composed chiefly ofacrylic resin (available under the tradename of Primal P376 from Rhomand Haas), 1 part by weight of clay and 0.01 part by weight ofdispersing agent (under the tradename of Primal 850) were mixed togetherand diluted by water to provide a viscosity of cp (25C). This liquid wasapplied to a raw sheet of paper by size pressing, to obtain a mastersheet.

In the apparatus shown in F168. 1, 2 or 3, the master sheet on themaster sheet holder drum is discharged therefrom when the last imagetransfer has been completed by the master sheet drum. To prevent themaster sheet drum from being stained or contaminated during that time,the printing sheet may desirably be fed excessively enough to overlapthe master sheet so that the two sheets may be removed in overlappingrelationship. Also, where no offset printing process takes place, theoptical system for illuminating the original image may be suitablychanged so that an electrophotographic copying process may be effecteddirectly on the printing sheet.

From the foregoing description, it will be appreciated that the presentinvention provides an apparatus which comprises a novel combination of aconventional offset printer unit and a conventional electrophotographiccopier unit, but which has eliminated all the drawbacks peculiar to bothunits and utilizes their advantages as well as their combined effect.Such an application of the electrophotographic copier unit leads to thepossibility of a master sheet for offset printing being producedreadilyand simply in a short time, and such an application of the offsetprinter unit enables multiple copies to be provided at a high speedwithout any time loss, which would otherwise occur in theelectrophotographic process.

Furthermore, the multiple copying operation effected by the offsetprinting technique does not include the liquid developing process asrequired for electrophotography, and this means that the use of thecarrier liquid occurs only until the'image is transferred from thephotosensitive drum to the master sheet, thus substantially eliminatingthe adverse effect of the gases, as produced from the carrier liquid.

. The electrophotographic process utilized with the present inventionhas been illustrated asCarlsons process, but it should be understoodthat the utilization of other various types of electrophotographicprocess is also within the scope of the present invention.

Summing up, the copying-printing apparatus of the present invention asdescribed above in detail may provide the following effects:

At least in operation, the production of the master sheet is notrequired in particular, and multiple copies can be produced within ashort time and with a greatly reduced consumption of the solvent, whichin turn leads to a well-maintained hygienic environment. Moreover, whenthe number of copies to be obtained is limited to one hundred sheets orso, the master paper in use need not be of a special type, such asconventional offset master paper, thus reducing the cost of the masterpaper and, accordingly, the cost incurred in copying.

We claim:

1. A copying-printing apparatus comprising a photosensitive member forrepetitive use, means for forming an electrostatic latent image on thesurface of said photosensitive member, means for developing saidelectrostatic latent image, means for supplying a master sheet, meansfor transferring said developed image onto said master sheet, aconductive elastic drum for retaining said master sheet for windingtherearound, means for applying a transfer bias voltage to said drum atleast when said developed image is transferred onto said master sheet,means for supplying ink to said master sheet, means for supplying aprinting sheet, and means for impressing said ink from said master sheetonto said printing sheet.

2. A copying-printing apparatus according to claim 1, wherein saiddeveloping means is a liquid developing device.

3. A copying-printing apparatus according to claim 2, wherein saidmaster sheet has a solvent resistivity of 0.14 to 25 seconds andsmoothness of 25 to seconds (according to Bekk indication).

4. A copying-printing apparatus according to claim 1, wherein saiddeveloping means is a dry type developing device.

5. A copying-printing apparatus according to claim 1, wherein saidphotosensitive member is in the form of cylindrical drum, and saiddeveloped image transfer means and said ink transfer means are providedby an area of contact between said two drums.

6. A copying-printing apparatus according to claim 1, wherein saidmaster sheet supply means is provided within said conductive elasticdrum.

7. A copying-printing apparatus according to claim 1, wherein saidphotosensitive medium and said master sheet holder member are in theform of cylindrical drums, and said developed image transfer means andsaid ink transfer means are provided by an area of contact between saidtwo drums.

8. A copying-printing apparatus comprising a photosensitive member forrepetitive use, means for forming an electrostatic latent image on thesurface of said photosensitive member, means for developing saidelectrostatic latent image, means for supplying sheet material capableof use selectively as a master sheet and as a printing sheet, means fortransferring said developed image onto said master sheet, a conductiveelastic drum for retaining said master sheet for winding therearound,means for applying a transfer bias voltage to said drum at least whensaid developed image is transferred onto said master sheet, means forsupplying ink to said master sheet, and means for impressing said inkfrom said master sheet onto said printing sheet.

9.. A copying-printing apparatus according to claim 8, wherein saidphotosensitive medium and said master sheet holder member are in theform of a cylindrical drum, and said developed image transfer means anding device.

1. A copying-printing apparatus comprising a photosensitive member forrepetitive use, means for forming an electrostatic latent image on thesurface of said photosensitive member, means for developing saidelectrostatic latent image, means for supplying a master sheet, meansfor transferring said developed image onto said master sheet, aconductive elastic drum for retaining said master sheet for windingtherearound, means for applying a transfer bias voltage to said drum atleast when said developed image is transferred onto said master sheet,means for supplying ink to said master sheet, means for supplying aprinting sheet, and means for impressing said ink from said master sheetonto said printing sheet.
 2. A copying-printing apparatus according toclaim 1, wherein said developing means is a liquid developing device. 3.A copying-printing apparatus according to claim 2, wherein said mastersheet has a solvent resistivity of 0.14 to 25 seconds and smoothness of25 to 150 seconds (according to Bekk indication).
 4. A copying-printingapparatus according to claim 1, wherein said developing means is a drytype developing device.
 5. A copying-printing apparatus according toclaim 1, wherein said photosensitive member is in the form ofcylindrical drum, and said developed image transfer means and said inktransfer means are provided by an area of contact between said twodrums.
 6. A copying-printing apparatus according to claim 1, whereinsaid master sheet supply means is provided within said conductiveelastic drum.
 7. A copying-printing apparatus according to claim 1,wherein said photosensitive medium and said master sheet holder memberare in the form of cylindrical drums, and said developed image transfermeans and said ink transfer means are provided by an area of contactbetween said two drums.
 8. A copying-printing apparatus comprising aphotosensitive member for repetitive use, means for forming anelectrostatic latent image on the surface of said photosensitive member,means for developing said electrostatic latent image, means forsupplying sheet material capable of use selectively as a master sheetand as a printing sheet, means for transferring said developed imageonto said master sheet, a conductive elastic drum for retaining saidmaster sheet for winding therearound, means for applying a transfer biasvoltage to said drum at least when said developed image is transferredonto said master sheet, means for supplying ink to said master sheet,and means for impressing said ink from said master sheet onto saidprinting sheet.
 9. A copying-printing apparatus according to claim 8,wherein said photosensitive medium and said master sheet holder memberare in the form of a cylindrical drum, and said developed image transfermeans and said ink transfer means are provided by an area of contactbetween said two drums.
 10. A copying-printing apparatus according toclaim 8, wherein said developing means is a liquid developing device.11. A copying-printing apparatus according to claim 10, wherein saidmaster sheet has a solvent resistivity of 0.14 to 25 seconds andsmoothness of 25 to 150 seconds (according to Bekk indication).
 12. Acopying-printing apparatus according to claim 8, wherein said developingmeans is a dry type developing device.